JP2000346924A - Gps receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a GPS receiver that can measure a position with high accuracy by excluding the influence of a multipath. SOLUTION: In step 205, when a satellite signal is received, a mean value EI is inverted to a positive value or a negative value according to whether a correlation result PI is a positive value or a negative value, and the mean value EI is normalized by the amplitude of the correlation value PI. In step 207, according to a first filter computing output, a code phase correction which controls a timing δ and a timing R which measure the phase and the amplitude of a pseudo noise generator is performed. In step 208, the correction amount of a code phase which is correlated by the code phase correction is input and time-integrated. When an error is added to the tracking of a pseudo noise code due to a multipath or the like, an integrated result by the computing processing operation of a second filter in the step 208 is changed. Since its change amount has a strong connection with an error in the tracking, the degree of its influence can be judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS (Global Positioning System) for receiving a signal from a positioning satellite and measuring a position.
stem) Receiver, especially NAVSTAR operated by the United States
By measuring the phase of a spread spectrum signal, such as a satellite or the GLONASS satellite operated by the Russian Federation, the time indicated by the satellite signal is measured, and for a receiver that determines the position, the received satellite signal is simulated. The present invention relates to a GPS receiver that samples in accordance with the timing of a noise code and measures the amplitude of a signal in association with a pseudo-noise code that accurately measures a position in a short time.

[0002]

2. Description of the Related Art In recent years, GPS receivers have been widely used as position sensors for car navigation systems, navigation devices for ships, and navigation devices for aircraft.

Conventionally, when measuring the phase difference of a pseudo-noise code between a receiver and a satellite, when the propagation path of the satellite signal is in a multipath state, the effect can be reduced.
GPS receivers are known. FIG.
Reference numeral 1 denotes a configuration of a conventional GPS receiver. In FIG. 11, the GPS satellite 1 transmits a GPS satellite signal (L1) having a carrier frequency of 1.57542 GHz for measuring a position.

The antenna 2 receives the radio wave of the GPS satellite 1, the filter 3 filters the satellite signal, the local oscillator 5 generates the local signal, and the mixer 6 mixes the output signal with the satellite signal. A mixer for outputting an intermediate frequency signal, a filter 7 is a filter for filtering only the intermediate frequency signal output from the mixer 6, a comparator 9 is a comparator for converting the intermediate frequency signal into a binary digital signal, and a latch 10 is A latch for sampling the digitized intermediate frequency signal, a local oscillator 11 is an oscillator for converting the frequency of the intermediate frequency signal to the baseband, a mixer 12 is a mixer for converting the frequency of the intermediate frequency signal to the baseband, and a filter 13 is a mixer. A filter for filtering components other than the baseband of the satellite signal from the output of the reference signal 12;
Is an oscillator for generating a reference clock of the receiver, and a multiplier 15 is a multiplier for multiplying the reference clock by four.

A pseudo noise generator 16 generates a pseudo noise code unique to each of a plurality of satellites, and a correlator 17 mixes a satellite signal and an output of the pseudo noise generator 16 for each of a plurality of satellites. A circuit that measures the correlation and samples the received signal in association with the pseudo-noise code generated by the pseudo-noise generator 16, a switch 18 switches a time-sequentially the output of the correlator 17 time-integrated for each satellite, The numerically controlled oscillator 19 is an oscillator that outputs the reproduced carrier wave tracking the carrier wave of the satellite signal in time sequence for each satellite, and the mixer 20 is a mixer that sequentially converts the output signal of the correlator 17 for each satellite into an orthogonal frequency. , Switch 21 is a switch for sequentially switching outputs I and Q of mixer 20, adder 22
And a RAM (random access memory) 23 constitute an accumulator that accumulates the output of the mixer 20 for each satellite.
Reference numeral 24 denotes a control unit that controls the pseudo-noise generator 16 and the numerically controlled oscillator 19 so as to track the satellite signal using the results of the cumulative addition of the in-phase component and the quadrature component separately for each satellite signal.

The operation of the conventional GPS receiver configured as described above will be described below. First, multiple G
The radio wave of the PS satellite 1 is received by the antenna 2. Next, an unnecessary signal is removed from the received signal by the filter 3 and amplified by the amplifier 4. Further, the frequency is converted by a frequency conversion circuit including the local oscillator 5, the mixer 6, and the filter 7. After the converted intermediate frequency signal is amplified and limited in amplitude by the amplifier 8,
The comparator 9 converts the signal into a binary logic signal. The binarized signal is sampled in the latch 10. The sampled signal undergoes quadrature frequency conversion by an I signal that matches the intermediate frequency output from the local oscillator 11 and a Q signal that is 90 ° out of phase with the I signal. Thereafter, independent signal processing is performed on the frequency-converted satellite signals I and Q for each satellite to be received.

[0007] The pseudo noise generator 16 outputs a pseudo noise code unique to each satellite to be received. This pseudo noise code unique to the satellite is called a C / A code and has a code rate of 1.02.
3 Mbps, code length 1023 chips, cycle is 1
msec. This pseudo noise code and the satellite signal I,
Q is mixed by the correlator 17 for each satellite to obtain a correlation. The phase of the pseudo noise code is quantized in units of the timing of a reference clock for signal processing, and the quantized value is set in the pseudo noise generator 16.

The correlator 17 mixes the received signal with the pseudo-noise code, smoothes it by time integration to a sampling frequency of several hundred KHz, outputs the smoothed signals A _I and A _Q, and outputs the pseudo-noise signal. The pseudo noise code generated by the generator is 0
The received signal sampled at the timing preceding or following by δ with respect to the timing of changing from
Signals B _I and B _Q smoothed by integration over a period corresponding to the sampling frequency of z are output.

The numerically controlled oscillator 19 oscillates a reproduced carrier signal for each satellite and outputs orthogonal output signals I and Q. With this output signal, the mixer 20 performs orthogonal frequency conversion on the smoothed output signal of the correlator 17. In this frequency conversion, since the sampling frequency of the input signal is low, a plurality of satellites are processed in a time division manner. The in-phase component I and quadrature component Q output from the mixer 20 are
Is converted to a time sequential signal.

An accumulator constituted by an adder 22 and a RAM 23
The product adder accumulates the output signal of the mixer 20 for each satellite.
I do. Signal A_I, A_QIs frequency-converted and the value obtained by cumulative addition is
Seki result P_I, P_QAnd signal B_I, B_QFrequency conversion and accumulation
The value obtained by adding the values is the average value E of the amplitude. _I, E_QAnd Period to be added
The interval is 1 msec from the beginning to the end of the C / A code
Is defined as one section.

The control unit 24 receives the result of the accumulation and controls the numerically controlled oscillator 19 so that the amplitude of the correlation result _PQ component is reduced, thereby tracking the carrier of the satellite signal. Further, by changing the δ measures the average value E _I of the amplitude, by looking for the value of δ average E _I of the amplitude is reduced, the pseudo noise generator 16 and the satellite signal, the pseudo noise code position Measure the phase difference.

[0012] processing the average value E _I amplitude find the value of the smaller δ is the average value EI, the value of the correlation result P _I is for positive, is provided with a mean value E _I to the control unit 24 Output to the low-pass filter, and if the value of the correlation result P _I is negative,
The average value E _I is inverted to positive and negative and output to this low-pass filter. If the time constant of the low-pass filter is increased, for example, to 30 seconds, the output of the low-pass filter becomes the average value E for each satellite.
It can be obtained further consequences not subjected accurate measure of the noise on _I.

By controlling δ and the phase of the pseudo-noise generator 16 so that the output of the low-pass filter becomes small, the satellite signal can be tracked with the pseudo-noise code. The control unit 24 also from positive and negative changes in the correlation result P _I component, demodulates the data of 50bps sent in BPSK modulation from the satellite. Then, the measured phase of the pseudo-noise code and 50 bps
Based on the data timing, the time at which the satellite emitted the radio wave is obtained. Further, the control unit 24 uses the orbit information and time information received for a plurality of satellites and the measured time to
The antenna position of the receiver is obtained by calculation and output to the outside.

Also, the amplitude characteristics are measured by sampling the received signal in advance, and even in a situation where there is multipath, the satellite signal is sampled and the amplitude characteristics are measured, and the characteristics are compared with the previously measured characteristics. Then, the phases and amplitudes of the direct wave and the reflected wave are predicted, and the pseudo noise code phase of the direct wave is accurately measured.

[0015]

However, in the above-mentioned conventional GPS receiver, when judging the state where multipath exists, the amplitude characteristic of the satellite signal measured in advance and the amplitude characteristic obtained by sampling the received signal are used. For comparison, very complicated processing was required, and a large-scale measuring circuit was required to sample the satellite signal in a short time to obtain the amplitude characteristic. Further, in the measurement of the phase of the carrier wave, since the signals A _I and A _Q obtained by mixing the received signal and the pseudo-noise code and performing time integration are used, there is a problem that the multi-path signal is greatly affected.

The present invention solves the above-mentioned conventional problems, and is capable of judging a multipath state by simple processing without using a large-scale measuring circuit, and capable of accurately measuring a carrier phase. It is intended to provide a GPS receiver.

[0017]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a first filter for obtaining a code phase correction amount for tracking a pseudo noise code of a satellite signal, and a phase correction amount for the first filter. In addition to the tracking filter for the pseudo-noise code constituted by means for correcting the phase of the pseudo-noise code, a second filter for integrating the phase correction amount with time, and the influence of multipath by the amplitude of the time-integrated result. Determining means for determining that the phase of the pseudo-noise code is changed by the influence of the multipath by means for determining the effect of the multipath, and removing the observation result affected by the pseudo-noise code. The position of the receiver is calculated based on the phase of the code.

The present invention also provides a local oscillator for generating a local oscillation signal tracked by a carrier signal, a means for frequency-converting a received signal with the local oscillation signal, and a fixed time difference with respect to the timing of the pseudo-noise code. Means for sampling the frequency-converted received signal by inverting the sign in the sign state and sampling the local-oscillation signal, which is the sampled received signal. Means for measuring the phase difference between the carrier wave of the received signal and the local oscillation signal at the converted timing, and corrects the phase of the local oscillation signal with the phase difference measured by the means for measuring the phase difference to perform observation. The carrier phase of the satellite signal.

As described above, even if the satellite tracking the pseudo-noise code includes a satellite affected by multipath, the position can be calculated by excluding it, and the accuracy of the pseudo-noise code based on the phase can be calculated. Good position measurement is possible. Also, in kinematic positioning, in which the relative position between a plurality of receivers is measured with high accuracy by comparing the phase of the carrier wave of the satellite signal, the influence of the delayed reflected signal can be reduced in measuring the phase of the carrier wave. G that can measure accurate position
A PS receiver is obtained.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The invention as set forth in claim 1 of the present invention comprises a local oscillator for tracking a carrier of a satellite signal, a pseudo-noise generator for generating a pseudo-noise code unique to a satellite, and a phase of the local oscillator. Means for controlling the phase of the pseudo-noise generator according to the change, and controlling the phase difference between the pseudo-noise code included in the satellite signal and the pseudo-noise code generated by the pseudo-noise generator to be constant, A correlator for measuring a phase difference of the pseudo-noise code, a first filter for inputting the measured phase difference and obtaining a correction amount of a code phase for correcting the phase difference of the pseudo-noise code, Means for correcting the phase of the pseudo-noise code, a second filter for time-integrating the correction amount, and means for determining the effect of multipath based on the amplitude of the time-integrated result. Means to do The GPS receiver is characterized in that the observation result affected by the multipath is excluded based on the determination result and the position of the receiver is calculated based on the phase of the pseudo-noise code. Even if a satellite signal is received, the observation result of this satellite is excluded, so that there is an effect that high position accuracy is obtained without being affected by multipath.

According to a second aspect of the present invention, in addition to a second filter for time-integrating the correction amount of the code phase and a means for judging the influence of multipath based on the amplitude of the time-integrated result, 2. The GPS according to claim 1, further comprising means for determining that the time has elapsed, and periodically initializing the second filter according to the determination.
It is a receiver that can quickly determine that the effect of multipath has been reduced, and uses the observation results of more satellites without being affected by multipath, and uses the phase of the pseudo-noise code. Has the effect that accurate position measurement can be performed.

According to a third aspect of the present invention, there is provided a means for evaluating a phase measurement error of a pseudo-noise code due to the influence of multipath, using an amplitude output from a second filter for time-integrating a correction amount of a code phase. 3. The GPS according to claim 1 or 2, wherein the position of the receiver is obtained from the observed value of the phase of the pseudo-noise code by the least square method weighted using the evaluation value of the phase measurement error. This is a receiver, and has an effect that a position can be obtained with higher frequency and accuracy according to the degree of influence of multipath.

The invention according to claim 4 provides a local oscillator for tracking a carrier of a satellite signal, a pseudo-noise generator for generating a pseudo-noise code unique to a satellite, and the pseudo-noise generator according to a phase change of the local oscillator. Means for controlling the phase of the noise generator so as to keep the phase difference between the pseudo-noise code included in the satellite signal and the pseudo-noise code generated by the pseudo-noise generator constant; A frequency converter for orthogonally transforming the signal, a means for generating a timing having a fixed time difference with respect to the timing of the pseudo noise code generated by the pseudo noise generator, and inverting the sign in the state of the code. Means for sampling the received signal output by the frequency converter, and the sampled timing with the in-phase component and the quadrature component with respect to the local oscillation signal which is the sampled received signal. Means for measuring the phase difference between the carrier wave of the received signal and the local oscillation signal in the local signal, and correcting the phase of the local oscillation signal by the phase difference measured by the means for measuring the phase difference to obtain the carrier wave phase of the satellite signal. A GPS receiver, wherein the phase of the local oscillation signal is corrected by the phase difference measured by the phase difference measuring means, and the observation value of the carrier wave phase of the satellite signal is obtained. By doing so, the effect of the delayed reflected signal can be reduced in the measurement of the carrier phase, so that there is an effect that the carrier phase of a satellite signal with less influence of multipath can be measured.

According to a fifth aspect of the present invention, there is provided a local oscillator for tracking a carrier wave of a satellite signal, a pseudo-noise generator for generating a pseudo-noise code unique to a satellite, and the pseudo-noise generator according to a phase change of the local oscillator. Means for controlling the phase of the noise generator so as to keep the phase difference between the pseudo-noise code included in the satellite signal and the pseudo-noise code generated by the pseudo-noise generator constant; A frequency converter for orthogonally transforming the signal, a means for generating a timing having a fixed time difference with respect to the timing of the pseudo noise code generated by the pseudo noise generator, and inverting the sign in the state of the code. A means for sampling the received signal output by the frequency converter is provided. If the sampled received signal has sufficient strength for tracking a carrier wave, the sampled signal corresponds to an orthogonal component of the local oscillation signal. The local oscillation signal is controlled so that the component of the sampled received signal becomes small, and if the sampled received signal is not of sufficient strength, a signal obtained by multiplying the received signal by the pseudo noise code and then performing time integration This is a GPS receiver characterized in that the local oscillation signal is controlled by the GPS receiver. When the reception sensitivity of the satellite signal is high, there is an effect that the influence of the multipath can be reduced in tracking the pseudo noise code.

According to a sixth aspect of the present invention, the local oscillation signal, which is a received signal sampled by holding the measurement result of each satellite individually and measuring the phase difference of the carrier near the rising edge of the pseudo-noise code, is stored. The phase difference measured by the in-phase component and the quadrature component with respect to the above is corrected in reverse by the stored phase difference of the corresponding satellite, and then corrects the phase of the local oscillation signal,
5. The GPS receiver according to claim 4, wherein the carrier phase is a carrier phase of the observed satellite signal, wherein the phase of the carrier near the rising edge of the pseudo noise code is slightly shifted from the average phase. Therefore, even when measuring the relative position with a receiver using another method, the effect is that not only can the relative position be measured accurately, but also the carrier phase of the satellite signal, which is less affected by multipath, can be measured. Have.

Further, the invention according to claim 7 provides a local oscillator for tracking a carrier of a satellite signal, a pseudo noise generator for generating a pseudo noise code unique to a satellite, and the pseudo oscillator according to a phase change of the local oscillator. Means for controlling the phase of the noise generator so as to keep the phase difference between the pseudo-noise code included in the satellite signal and the pseudo-noise code generated by the pseudo-noise generator constant; A frequency converter for orthogonally transforming the signal, a means for generating a timing having a fixed time difference with respect to the timing of the pseudo noise code generated by the pseudo noise generator, and inverting the sign in the state of the code. Means for sampling the received signal output by the frequency converter, and the sampled timing with the in-phase component and the quadrature component with respect to the local oscillation signal which is the sampled received signal. Means for measuring the phase difference between the carrier of the received signal and the local oscillation signal in the receiver, preliminarily measuring the phase difference of the carrier near the rising edge of the pseudo-noise code, holding the measurement result individually for each satellite, and measuring the position. When again measuring the phase difference of the carrier near the rising edge of the pseudo-noise code,
Determine the effect of multipath by comparing with the stored phase difference of the corresponding satellite, eliminate the observations affected by multipath, and calculate the position of the receiver with the phase of the pseudo-noise code This is a GPS receiver characterized by the fact that even if a satellite signal affected by multipath is received, the observation result of this satellite is excluded, so that the operation is not affected by multipath. Have.

The invention according to claim 8 is a means for judging the influence of multipath according to any one of claims 1 to 3, or evaluates a phase measurement error of a pseudo-noise code due to the influence of multipath. In addition to the means, a frequency converter that performs orthogonal frequency conversion of a received signal with a local oscillation signal, and a timing of a pseudo noise code generated by a pseudo noise generator,
A means for generating a timing having a fixed time difference, a means for sampling a reception signal output by the frequency converter in which the sign is inverted in the state of the sign, and a local oscillation signal which is the sampled reception signal. A means for measuring the phase difference between the carrier of the received signal and the local oscillation signal at the sampled timing with the in-phase component and the quadrature component with respect to the phase difference is provided, and the phase difference of the carrier is measured in advance near the rising edge of the pseudo noise code, This measurement result is held individually for each satellite, and when measuring the position, the phase difference of the carrier is measured again near the rising edge of the pseudo-noise code, and compared with the stored phase difference of the corresponding satellite. 4. The GPS receiving device according to claim 1, wherein the most severe condition is selected from the plurality of multipath evaluation results. Is obtained by a machine, the observation of the satellite signal affected by multipath, such an action can changing more reliably eliminate or weighting.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This is explained using FIG.

(First Embodiment) FIG. 1 shows a configuration of a GPS receiver for measuring the amplitude of a signal in association with a pseudo-noise code, which is similar to the conventional example of FIG. The method of tracking the pseudo-noise code is different. FIG.
In the GPS satellite 101, a GPS satellite signal (L) having a carrier frequency of 1.57542 GHz for measuring the position is used.
1) is being transmitted.

An antenna 102 is a non-directional antenna for receiving radio waves from a GPS satellite, a filter 103 is a band filter having a frequency of 1.57542 GHz and a bandwidth of 30 MHz for filtering satellite signals, and an amplifier 104 is a frequency 1.57542 GHz.
z-band amplifier, local oscillator 105 is 1.608156GH
An oscillator for generating a local signal of z, a mixer 106 is a mixer for mixing the output signal and the satellite signal to output an intermediate frequency signal, and a filter 107 is 32.736 MH output from the mixer.
a band filter for filtering only an intermediate frequency signal having a bandwidth of 8 MHz at z, an amplifier 108 for amplifying the intermediate frequency signal, a comparator 109 for converting the intermediate frequency signal into a binary digital signal, A latch for sampling the digitized intermediate frequency signal at a frequency of 65.472 MHz, a local oscillator 111 is a circuit for generating an orthogonal local signal 32.736 MHz for frequency-converting the intermediate frequency signal to a baseband, and a mixer 112 is a local oscillator. A mixer for mixing the output of 111 and the intermediate frequency signal, a filter 113 is a low-pass filter for converting a signal sampled at 65.472 MHz to a signal sampled at 16.368 MHz, and a reference oscillator 114 is a reference clock of the receiver. Generated oscillator, multiplier 115 is reference oscillator 1
This is a PLL oscillator that multiplies the output of 14 by four.

The pseudo-noise generator 116 generates a pseudo-noise code unique to each of a plurality of satellites, and the correlator 117 mixes the satellite signal and the output of the pseudo-noise generator 116 for each of the plurality of satellites. A circuit for measuring the correlation and sampling the received signal in association with the pseudo-noise code generated by the pseudo-noise generator 116, a switch 118
Is a switch for sequentially switching the output of the correlator 117, which is time-integrated for each satellite, and a numerically controlled oscillator 119 is an oscillator for outputting a reproduced carrier wave tracking the carrier wave of the satellite signal for each satellite in time sequence. Is a mixer for sequentially converting the output signal of the correlator 117 into orthogonal frequency for each satellite, a switch 121 is a switch for sequentially switching and outputting the outputs I and Q of the mixer, an adder 122 and a RAM (random access memory) 123 are A cumulative adder that accumulates and adds the output of the mixer 120 for each satellite, the control unit 124 uses the result of the cumulative addition separately for the in-phase component and the quadrature component for each satellite signal to track the satellite signal. This is a control circuit using a microprocessor for controlling the pseudo noise generator 116 and the numerically controlled oscillator 119.

The operation of the GPS receiver configured as described above will be described below. The configuration is the same as the conventional example of FIG. 11, but the operation of the control unit 124 is different. First, radio waves of a plurality of GPS satellites 101 are received by an antenna 102. Next, an unnecessary signal is removed from the received signal by the filter 103 and amplified by the amplifier 104. Furthermore, the local oscillator 105,
Frequency conversion is performed by a frequency conversion circuit including the mixer 106 and the filter 107. The frequency of the output intermediate frequency signal is 3
This signal is centered at 2.736 MHz.

Next, the converted intermediate frequency signal is
After the amplification and the amplitude limitation, the comparator 109 converts the signal into a binary logic signal. The binarized signal is output from the latch 110 to the 65.472M output by the quadrupler 115.
The sampling is performed with a clock signal of Hz. Thereafter, all signals are processed as discrete values by a logic circuit or an arithmetic circuit. This sampled signal is combined with a 32.736 MHz I signal output from the local oscillator 111 and a 9
Orthogonal frequency conversion is performed by Q signals having different 0 ° phases.
Further, regarding the frequency-converted satellite signals I and Q,
Independent signal processing is performed for each receiving satellite.

The pseudo noise generator 116 outputs a pseudo noise code unique to each satellite to be received. This pseudo noise code unique to the satellite is called a C / A code and has a code rate of 1.0.
23 Mbps, code length 1023 chips, cycle is 1 msec. The pseudo noise code and the intermediate frequency signals I and Q are mixed by a correlator 117 for each satellite to obtain a correlation. The phase of the pseudo-noise code is quantized in units of 16.368 MHz timing (corresponding to 1/16 chip of the pseudo-noise code), which is a reference clock for signal processing, and this quantized value is set in the pseudo-noise generator 116. I do.

The correlator 117 mixes the received signal with the pseudo-noise code, smoothes it by time integration to a sampling frequency of several hundred KHz, outputs the smoothed signals A _I and A _Q, and outputs the pseudo-noise signal. The pseudo-noise code generated by the generator is
A received signal sampled at a timing preceding or succeeding by δ with respect to the timing of changing from 0 to 1 is several hundred K
The signals B _I and B _Q smoothed by integration over a period corresponding to a sampling frequency of Hz are output.

The numerically controlled oscillator 119 oscillates a reproduced carrier signal for each satellite and outputs orthogonal output signals I and Q. Based on the output signal, the mixer 120 performs orthogonal frequency conversion on the smoothed output signal of the correlator 117. In this frequency conversion, since the sampling frequency of the input signal is low, a plurality of satellites are processed in a time division manner.

The in-phase component I and the quadrature component Q output from the mixer 120 are converted by the switch 121 into time-sequential signals. Then, a cumulative adder composed of the adder 122 and the RAM 123 cumulatively adds the output signal of the mixer 120 for each satellite. The values obtained by frequency-converting and cumulatively adding the signals A _I and A _Q are used as correlation results P _I and P _Q, and the values obtained by frequency-converting the signals B _I and B _Q and cumulatively adding are used as average amplitude values E _I and E _Q. . The period of addition is 1 msec from the beginning to the end of the C / A code.

The control unit 124 receives the cumulative addition result,
By controlling the numerically controlled oscillator 119 so that the amplitude of the correlation result _PQ component is reduced, the carrier of the satellite signal is tracked. Further, the average value E _I of the amplitude is measured while changing the phase of δ and the phase of the pseudo noise generator 116, and the phase of the pseudo noise code is tracked so that the average value E _{I of the} amplitude becomes small. Then, by adding the measured phase difference to the phase set in the pseudo noise generator 116, the phase of the pseudo noise code included in the satellite signal is measured.

The control unit 124 also sent from the positive and negative changes in the correlation result P _I component, with BPSK modulation from the satellite 50bps
Demodulate the data. Then, based on the measured phase of the pseudo-noise code and the timing of the 50 bps data, the time at which the satellite emits radio waves is determined.

Further, the control unit 124 uses the orbital information and time information received for a plurality of satellites and the measured time to calculate the GPS time, which is the sum of the time at which each satellite emitted a radio wave and the propagation time to the receiving position. An antenna position of the receiver that is equal is obtained by calculation and output to the outside.

FIG. 2 shows a detailed configuration of the correlator 117 shown in FIG. 1. In FIG. 2, the counter 125 is provided by the pseudo noise generator 1 shown in FIG.
The transition timing signal of the pseudo noise code which is eight reference clocks ahead of the pseudo noise code generated by the counter 16 is counted, and the pseudo noise code preceding or succeeding by δ with respect to the transition timing of the coincident pseudo noise code is started. And a signal indicating the next timing and a signal identifying the two timings.

A counter 126 is a counting circuit for generating a timing coincident with the pseudo noise generator 116, and a latch 127 is a D-latch for holding a pseudo noise code by a timing signal generated by the pseudo noise generator 116 and preceding by eight reference clocks. , A latch 128 holds a pseudo-noise code at the timing output from the counter 126 and a timing coincident with the pseudo-noise generator 116, and a logic circuit 129 outputs a pseudo-noise code preceding by eight clocks and a pseudo-noise code following eight clocks. The noise code is input, and as shown in Table 1 below, 1 is set according to the difference between the two inputs.
Or a circuit that outputs -1.

<Table 1> preceding code input A succeeding code input BY output 0 0 0 1 0 -1 0 1 1 1 1 0

The mixer 130 includes a multiplier and a filter for inverting the sign of the output signal of the filter 113 in FIG. 1 depending on whether the pseudo noise code corresponding to the same timing as the pseudo noise generator 116 output from the latch 128 is 1 or 0. 131 is the output I of the mixer 130
And Q are time integrated, and the sampling frequency is several hundred KHz.
The accumulator and the weighting unit 132 that output the smoothed signals A _I and A _Q of the value
A weighting device that weights the output signal of the filter 113 in FIG. 1 in accordance with the signal for identifying the timing of the preceding and succeeding lines output by the mixer 133. The mixer 133 multiplies the output of the logic circuit 129 by the output signal of the filter 113 in FIG. When a signal indicating a timing preceding or succeeding by δ output from the counter 125 and a signal indicating the next timing are input, the filter 134 integrates the output of the mixer 133 and the sampling frequency is increased to several hundred KHz. It is a cumulative adder that outputs correspondingly smoothed signals _BI and _BQ .

The operation of the correlator 117 of FIG. 1 configured as described above will be described below with reference to the configuration of the correlator 117 of FIG. 2, the timing chart of FIG. 3, and the amplitude characteristic of FIG. FIG.
(A) is a pseudo-noise code that is eight reference clocks ahead of the pseudo-noise code input from the pseudo-noise generator 116. FIG. 3B shows the pseudo-noise code output from the latch 128, which has the same timing as the pseudo-noise code generated by the pseudo-noise generator 116.

When the output of the latch 128 is 0, the mixer 130 inverts the sign of the satellite signal received from the filter 113 and outputs the inverted signal. When it is 1, the mixer 130 outputs the satellite signal as it is. The filter 133 outputs the signals A _I and A _Q smoothed as described above. Further, this signal becomes correlation results P _I and P _Q by frequency conversion and cumulative addition. It is assumed that the pseudo-noise code corresponding to the coincident timing has the same kind of code as the pseudo-noise code of the received satellite signal, and the phases thereof are substantially the same. The satellite signal being received at this time is
At 130, the spread spectrum signal is despread,
A BPSK-modulated phase-modulated signal at 50 bps can be obtained.

The control unit 124 tracks the carrier of the satellite signal by controlling the numerically controlled oscillator 119 so that the orthogonal component P _Q of the correlation result output from the filter 131 is reduced. Further, the phase modulation signal is demodulated by examining whether the in-phase component P _I of the correlation result changes between positive and negative, and the time information and the orbit information time are received from the satellite signal.

FIG. 3C shows a signal output from the logic circuit 129. The eight clocks before and after the timing when the pseudo noise code (b) generated by the pseudo noise generator 116 changes to 1 are -1, 0. 7 clocks before and after the timing of changing to 1. FIG. 3D shows a signal indicating the timing of the pseudo-noise code preceding the transition timing of the pseudo-noise code by δ = −2 and the next timing, and the filter 134 receives the signal for two clocks. The output of the mixer 133 is integrated. However, the output of the mixer 133 is 0 at the timing when the pseudo noise code (b) generated by the pseudo noise generator 116 does not change. FIG. 3E shows a signal for identifying the first half and the second half of FIG. 3D.

The control unit 124 changes the timing by changing the count value of the counter 125. The timing δ of the preceding or following pseudo noise code can be set by the number of reference clocks, and is an integer value from -7 to 7.

The control section 124 in FIG. 1 measures the amplitude of the satellite signal in accordance with the timing of the pseudo noise code of the satellite signal being tracked. The timing for measuring the amplitude is determined relatively to the phase of the pseudo-noise code being tracked. The pseudo-noise code is 1/16 of the reference clock generated by the receiver.
However, since the frequency error of the reference clock and the distance between the receiver and the satellite change, the phase of the pseudo-noise code changes with time in tracking the pseudo-noise code. In addition,
The amount of this phase change can be measured fairly accurately by tracking the carrier, and this observation is used to control the tracking of the pseudo-noise code.

Therefore, the relationship between the timing of the change of the pseudo noise code and the timing of the reference clock gradually changes. The control unit 124 further calculates the phase of the pseudo-noise code in which the timing for measuring the amplitude of the satellite signal is corrected with respect to the changing timing. Then, for tracking the pseudo-noise code, the pseudo-noise generator 116 is controlled with the phase of the integer value quantized at the cycle of the reference clock. Therefore, the phase of the pseudo-noise code set by the control unit 124 is rounded down to a small number when quantizing in units of 1/16 chip.

The timing for measuring the amplitude of the satellite signal in relation to the pseudo noise code is set based on the relationship between the phase corrected for the measured timing and the phase set for the pseudo noise generator 116. Δ corresponding to the timing at which the amplitude is to be measured is determined. This δ is also 1/16
Since it is a chip unit, there is a part of the number that is rounded down at the time of quantization and is defined as R. Of course, R is in the range of 0 chip to 1/16 chip or less. The obtained value of δ is set in the counter 125. On the other hand, according to the obtained value R, the control unit 124 outputs two pieces of weighted data to the weighting unit 132.

The weighting method is shown in FIG.
Mining is a value proportional to (1.0-R), 0 timing
Is a value proportional to R. This weighted signal is
Output signal B of filter 134_I, B_QOutput as
Average value E of added amplitude_I, E _QBecomes

FIG. 4 shows the timing δ and the pseudo noise generator 11.
Controls 6 phase obtained when changing the timing of the pseudo-noise code and an amplitude characteristic showing a change in the E _I. The horizontal axis represents the phase difference between the timing of the satellite signal and the timing at which the amplitude was observed, and the vertical axis represents the amplitude of the satellite signal obtained at the observation timing, which is a relative value with the maximum amplitude being 1. In addition, 50 bps added to the satellite signal
The waveform of this waveform is inverted between positive and negative. The phase difference between the satellite signal and the pseudo-noise code between the receiver and the phase difference is 0 where the amplitude becomes 0 at the center of the amplitude characteristic.

FIG. 5 is a flowchart for explaining a method of tracking a pseudo-noise code in the control unit 124, which is unique to the present embodiment. In step 201 of FIG. 5, each measured value of the correlation result P _I and the average value E _I of the amplitude is received. In step 202, the amplitude of each measured value is determined to determine whether a satellite signal has been received. If the satellite signal has not been received, it is determined in step 203 whether or not to continue tracking the satellite signal. When the tracking of the satellite signal is interrupted in step 203, the pull-in mode is changed in step 204.

On the other hand, if the satellite signal has been received, in step 205, the average value E _I is inverted by the sign of the correlation result P _I , and the average value E _I is normalized by the amplitude of P _I. Next, in step 206, the average value E _I standardized in step 205 is input, and the noise component is removed by a low-pass filter having a time constant τ1 of 10 minutes.

In step 207, the first in step 206
The code phase correction for controlling the timings .delta. And R for measuring the phase and amplitude of the pseudo noise generator 116 is performed according to the filter operation output of. Next, in step 208, the correction amount of the code phase corrected by the code phase correction in step 207 is input and time integrated. In step 209, the absolute value of the second filter operation output in step 208 is compared with the previous maximum value M, and the larger one is output as the next maximum value M, and the maximum value M is held.

In step 210, the value of the maximum value M is attenuated at a constant rate. Then, in step 211, the maximum value M is compared with a predetermined value to determine the maximum value. Steps
At 212, a flag-on process is performed to set a flag indicating a multipath environment when the maximum value M exceeds a predetermined value. Then, in step 213, when the maximum value M falls below a predetermined value, a flag-off process for defeating a flag indicating the multipath environment is performed, and in step 214, the process ends.

In this processing flow, the operation of the first filter in step 206 and the tracking of the pseudo-noise code by the code phase correction in step 207 are performed in a low frequency band with respect to the phase noise of the pseudo-noise code included in the received signal. Acts as a pass filter. Further, in the time integration by the arithmetic processing of the second filter in step 208, it is possible to know the amount of code phase correction from the past to that time.

The phase change of the pseudo-noise code caused by the change in distance between the satellite and the receiver reflects the phase change of the carrier wave in the phase of the pseudo-noise code as described above. During this operation, the time integration value keeps a substantially constant value. When it is determined that tracking is stable, the calculation processing of the second filter in step 208 is initialized to 0, so that the value becomes approximately 0.

If an error is added to the tracking of the pseudo-noise code due to factors such as multipath, the result of the integration performed by the second filter in step 208 changes. Since this change has a strong relationship with the error in tracking,
The degree of the influence can be determined. When the influence exceeds the required measurement accuracy, the predetermined value is determined so that it can be determined by the maximum value determination in step 211, and when the position is measured via a flag indicating a multipath environment, the multiplicity is determined. Eliminate observations from satellites affected by the path.

As described above, according to the first embodiment of the present invention, the amplitude characteristic of a satellite signal measured in advance is compared with the amplitude characteristic obtained by sampling a received signal, which is a very complicated example of the conventional example. A first filter for obtaining a correction amount of a code phase in tracking a pseudo noise code of a satellite signal,
A second filter that integrates the amount of phase correction with respect to the tracking filter of the pseudo-noise code configured by means for correcting the phase of the pseudo-noise code with the amount of phase correction, and an amplitude of the result of the time integration. By providing a means for determining the effect of multipath, it is possible to detect the phase of the pseudo-noise code under the influence of multipath with very simple processing, and calculate the position of the affected observation result. Therefore, an excellent effect can be obtained in that accurate position measurement based on the phase of the pseudo-noise code can be performed without being affected by multipath.

The correlator 117 of this embodiment has a characteristic that the phase of the pseudo-noise code is hardly affected by multipath, and includes a first filter for obtaining a code phase correction amount,
The tracking filter of the pseudo-noise code constituted by the means for correcting the phase of the pseudo-noise code by the amount of phase correction also reduces the component of the pseudo-noise code, which is caused by multipath, showing a relatively fast time change of the phase noise. However, when the number of satellites that can be received is large, it is more effective to eliminate the observation results of the satellites affected by the multipath to some extent because higher accuracy is obtained and the processing is simpler, so that the effect is large.

(Second Embodiment) The configuration of the second embodiment is the same as that of the first embodiment shown in FIG. 1, but the operation of the control unit 124 is different. FIG. 6 is a flowchart illustrating a method of tracking a pseudo-noise generating code in the control unit 124, which is unique to the present embodiment. In FIG. 6, the processing flow and the operation are substantially the same as those in the flow chart of FIG. 5 illustrating the operation of the first embodiment, but when the maximum value M exceeds a predetermined value in step 212, the multipath Subsequent to the flag-on processing step of setting a flag indicating the environment, a time determination processing step of determining whether five minutes have elapsed when the flag is set in step 215, and a second determination in step 216 each time five minutes have elapsed. Is provided in the step of initializing the operation in the filter of FIG.

In the first embodiment as well, when it is determined that the tracking is stable, although not shown in the flow chart of FIG. 5, the operation of the second filter is initialized. At the time of this initialization, if the multipath is not affected by the multipath, if the multipath is affected after that, or if the influence of the multipath is lessened thereafter, the multipath is immediately performed. The state of the influence of can be detected. However, if the influence of the multipath is affected when the tracking is stably initialized, the determination when the influence of the multipath is reduced becomes slow.

FIG. 7A shows a case where the tracking is stabilized and initialization of the arithmetic processing of the second filter is performed in a situation where the multipath is affected in the first embodiment. 7 is a graph showing a calculation output of the second filter. The vertical axis is the amplitude of the operation output of the second filter, and the unit is one chip of the pseudo noise code phase. The input to the second filter is the amount of phase correction of the pseudo-noise code, which is the phase change of the pseudo-noise code in tracking, and corresponds to the amount of deviation from the phase change of the carrier. The horizontal axis indicates the time when tracking is stable
This is the elapsed time in minutes.

In FIG. 7A, at time 301, the effect of multipath is reduced. However, since the phase of the pseudo-noise code at the time of initialization is shifted, the value is settled with an offset. Although the offset can be gradually eliminated by means for attenuating the DC component by the second filter operation with a long time constant, it takes time to recognize this state after the influence of multipath is reduced.

On the other hand, FIG. 7B is a graph showing the calculation output of the second filter in the second embodiment under the same multipath influence as in FIG. 7A. It is. The vertical axis an amplitude of the calculated output of the second filter was normalized by the amplitude of P _I, which corresponds to a phase change of the pseudo-noise code. The horizontal axis represents the time elapsed based on the time when tracking is stabilized.

In FIG. 7B, after the tracking is stabilized, it is determined in the maximum value determination processing in step 211 that the influence of the multipath is large. Thereafter, the arithmetic processing of the second filter is initialized to 0 every 5 minutes, but before the maximum value M attenuates and falls below a predetermined value in the maximum value determination processing in step 211, the second filter is initialized. The absolute value of the calculation output has exceeded the previous maximum value M, and the maximum value M has increased in the maximum value holding process in step 209. Further, the influence of the multipath decreases as time further elapses, and at time 301, the maximum value M attenuates, and it is determined in the maximum value determination processing in step 211 that the influence of the multipath has decreased.

As described above, according to the second embodiment of the present invention, the second filter for integrating the correction amount of the phase with respect to the tracking filter of the pseudo-noise code and the amplitude of the result of the time integration are obtained. Means for determining whether a predetermined time has elapsed and means for initializing the second filter in accordance with this determination in addition to the means for determining the effect of multipath, thereby reducing the effect of multipath. Since it is possible to quickly judge that an error has occurred, an excellent effect can be obtained in that accurate position measurement can be performed by the pseudo noise code phase using the observation results of more satellites without being affected by multipath. .

(Third Embodiment) The configuration of the third embodiment is the same as that of the first embodiment shown in FIG. 1, but the operation of the control unit 124 is different. FIG. 8 is a flowchart illustrating a method of tracking a pseudo-noise code in the control unit 124, which is unique to the present embodiment. In FIG. 8, the processing flow and operation are substantially the same as those in the flow chart of FIG. 6 for explaining the operation of the second embodiment, but the maximum value determination processing in step 211 in FIG. The difference is that an error evaluation process in step 217 is provided instead of the flag-off process in step 213.

The input of the second filter is the amount of phase correction of the pseudo-noise code, and the amplitude of the operation output of the second filter is a value obtained by integrating this value. Yes, and corresponds to a deviation from the phase change of the carrier. If the intensity of the reflected wave in the multipath is weaker than that of the direct wave and no phase slip occurs in tracking the carrier, the change in the phase of the tracked carrier corresponds to the change in the distance to the satellite. Therefore, the degree of the phase change of the pseudo-noise code due to multipath can be evaluated by the amplitude of the operation output of the second filter.

In the error evaluation processing in step 217,
In the maximum value holding process in step 209, the absolute value of the operation output of the second filter is obtained, and the larger value than the previous maximum value M is set as the next maximum value M.
/ 4 is output as an error evaluation value. The phase error of the observed pseudo-noise code is determined by adding the satellite time error, the ionospheric error, and the like to the evaluation value of the error for each satellite.

Then, using the phases of all the observed pseudo-noise codes, weighting is performed by the error of the phase of the pseudo-noise codes, and the position of the receiver is obtained by the least square method. Therefore, when the number of satellites that can be received is small, observation results of satellites that are expected to have large errors due to multipath also contribute to determining the position, but errors in positioning results increase. On the other hand, when the number of satellites that can be received is large, the contribution of observation results of satellites that are expected to have many errors due to multipath becomes small, and the position can be determined with high accuracy without being affected by errors due to multipath. Moreover, the difference between the two can be automatically optimized by calculation.

As described above, according to the third embodiment of the present invention, the phase measurement error of the pseudo-noise code due to the influence of multipath is replaced with the means for determining the influence of multipath based on the amplitude obtained as a result of time integration. Means for evaluating the position of the receiver by weighting using the evaluation value of the phase measurement error and obtaining the position of the receiver by the least square method from the observed value of the phase of the pseudo-noise code. Thus, the position can be obtained with higher accuracy and appropriate accuracy.

(Fourth Embodiment) The configuration of the fourth embodiment is the same as that of the first embodiment shown in FIG. 1, but the detailed configuration of the correlator 117 is different. FIG. 9 shows a detailed configuration of the correlator 117 unique to the present embodiment.
The difference from the detailed configuration of the correlator will be described.

In FIG. 9, a mixer 135 inverts the sign of the output signal of the weighter 132 depending on whether the pseudo noise code preceding the reference clock eight is 1 or 0.
When a signal indicating the timing preceding or succeeding by δ output from the counter 125 and the next timing are input, the output of the mixer 135 is integrated to perform smoothing corresponding to a sampling frequency of several hundred KHz. It is a cumulative adder that outputs the applied signals C _I and C _Q.

Using the amplitude characteristic of FIG. 10, the correlator 11 of FIG.
The operation of 7 will be described below. It is assumed that the received satellite signal is only a direct wave, and the pseudo-noise generator 116 accurately tracks the pseudo-noise code of the satellite signal. The tracking of the pseudo-noise code is performed by the configuration other than the mixer 135 and the filter 136 in the same manner as the operation of the first embodiment shown in FIG. Filter 136 operates similarly to filter 134, but with a different input signal.

The signal output from the weighting unit 132 is
The signals are integrated by the filter 136 through 35, and the output signals C _I , C
Output as _Q. The accumulator constituted by the adder 122 and the RAM 123 shown in FIG. 1 outputs the output signal C similarly to the average values E _I and E _Q.
I and C _Q are cumulatively added for each satellite. The values obtained by the frequency conversion and the cumulative addition are defined as average amplitude values G _I and G _Q. The addition period is 1 msec from the beginning to the end of the C / A code.
Let c be one section.

[0080] FIG. 10 (a), obtained when changing the timing of the pseudo-noise code by controlling the phase of the timing δ and a pseudo-noise generator 116, an amplitude characteristic showing a change in G _I. The amplitude of G _Q can be expected to be approximately zero. However, it is assumed that the bandwidth of the filter 107 is sufficiently wider than the bandwidth of the satellite signal. The horizontal axis represents the phase difference between the timing of the satellite signal and the timing at which the amplitude was observed, and the vertical axis represents the amplitude of the satellite signal obtained at the observation timing, which is a relative value with the maximum amplitude being 1. The waveform is inverted between positive and negative due to the 50 bps phase modulation applied to the satellite signal. The amplitude is expected to be approximately 0.5 where the phase difference of the pseudo noise code between the satellite signal and the receiver is zero. FIG. 4 shows the amplitude characteristics when the pseudo-noise code changes from 0 to 1 or from 1 to 0. The amplitude characteristics in FIG. 10A correspond to the amplitude characteristics of one pseudo-noise code alone.

In the following, in this embodiment, the kinematic positioning for measuring the phases of the carrier waves for a plurality of satellites, comparing the measured phases of the carrier waves among a plurality of receivers, and measuring the relative positions of the plurality of receivers will be described. This is a description of a method of measuring a carrier phase for performing the following.

First, tracking is performed on the carrier of the satellite signal and the pseudo noise code. At the same time as measuring the relative position, the numerically controlled oscillator
Measure the phase of 119. At the same time, to measure G _I and G _Q at the timing corresponding to the phase difference 0 of the amplitude characteristic.
To match this timing, the pseudo noise code is tracked so that the average value EI of the amplitude becomes zero. G _I and G _Q obtained here correspond to the satellite signal sampled at the rising portion synchronized with the pseudo noise code, but at the rising portion of the pseudo noise code with respect to the average carrier phase being tracked. It can be seen that it is responsible for the local carrier phase difference. Then, the measured phase of the numerically controlled oscillator 119 is corrected by an amount corresponding to the phase determined by G _I and G _Q , and the corrected phase is output as the observed value of the carrier wave phase.
The phase after the correction is the local carrier phase observed at the rising portion of the pseudo-noise code.

FIG. 10 (b) shows a multipath state in which a direct wave of a received satellite signal includes a reflected wave having an amplitude of 1/2 which is delayed by 1/2 chip of the direct wave. obtained when changing the timing of the pseudo-noise code to control the phase of the generator 116, an amplitude characteristic showing a change in G _I. The solid line assumes the case of the phase of the carrier wave acting additively, and the dotted line assumes the case of the phase of the carrier wave acting subtractively. Other carrier phases exhibit characteristics between the two. However, although the overall amplitude also changes, the first half amplitude is also shown for easy understanding. FIG. 10 (b)
As apparent from the above, the average values G _I and G _Q are not affected by the reflected signal when the phase difference between the pseudo noise codes is near zero.

As described above, according to the fourth embodiment of the present invention, the reception signal frequency-converted by the local oscillation signal that tracks the carrier signal is converted with respect to the timing of the pseudo noise code.
At a timing having a certain time difference, the received signal whose sign is inverted in the sign state is sampled, and the in-phase component and the quadrature component of the local oscillation signal, which is the sampled received signal,
A means for measuring the phase difference between the carrier wave of the received signal and the local oscillation signal at the sampled timing is provided, and the phase of the local oscillation signal is corrected by the phase difference measured by the means for measuring the phase difference. Since the carrier wave phase of the observed satellite signal is used, an excellent effect is obtained in that the carrier wave phase of the satellite signal which is less affected by multipath can be measured.

(Fifth Embodiment) The configuration of the fifth embodiment is the same as that of the fourth embodiment in FIG. 9, but the operation of the control unit 124 is different. In the above-described fourth embodiment, the control unit 124 outputs the signals A _I ,
By controlling the numerically controlled oscillator 119 so that the amplitude of the P _Q component of the correlation result of adding accumulated frequency conversion of the A _Q decreases to track the carrier of the satellite signal.

On the other hand, in the present embodiment, the correlator 117
The amplitudes of the G _I and G _Q components of the correlation result obtained by frequency-converting and cumulatively adding the signals C _I and C _Q output by
If the _I component and the G _Q component can be measured accurately in phase by controlling the numerically controlled oscillator 119 so that the amplitude of the G _Q components not P _Q component of the correlation result becomes smaller, to track the carrier of the satellite signal .

G of correlation result_IIngredients and G_QSmall component amplitude
G in short time_IIngredients and G_QAccurate phase measurement from components
If it cannot be determined, the same as in the above fourth embodiment
To P _QNumerically controlled oscillator 119 to reduce the component amplitude
Control.

Since the G _I component and the G _Q component are sampled from the satellite signal and then integrated for 1 msec, the S / N is worse than P _I and P _Q of the correlation results that are continuously integrated. Therefore, when a fast response speed is required for tracking a carrier wave, the operation is more stable by tracking with P _I and P _Q. However, the influence of multi-path, less is better to tracking by G _I and G _Q.
In a multipath environment, if the phase of the local oscillator matches the direct wave, not only can the carrier phase of the satellite signal, which is less affected by the multipath, be measured, but also the tracking of the pseudo noise code Since the component of the reflected wave orthogonal to the above can be eliminated, the influence of multipath can be reduced.

As described above, according to the fifth embodiment of the present invention, the reception signal frequency-converted by the local oscillation signal that tracks the carrier signal is converted with respect to the timing of the pseudo-noise code.
At a timing having a certain time difference, the received signal whose sign is inverted in the sign state is sampled, and when the sampled received signal is strong, the local signal is reduced so that the quadrature component of the sampled received signal is reduced. When the oscillation signal is controlled and the sampled reception signal is weak, the local oscillation signal is controlled by a signal obtained by multiplying the reception signal by the pseudo noise code and then performing time integration. An excellent effect is obtained in that the effect of multipath can be reduced in tracking the pseudo-noise code.

(Sixth Embodiment) The configuration of the sixth embodiment is the same as that of the fourth embodiment shown in FIG. 9, but the operation of the control unit 124 is different. The schematic operation is also the same as that of the above-described fourth embodiment, and only the differences will be described below.

First, when it is determined that there is no multipath,
Measuring the G _I and G _Q as in the fourth embodiment described at the timing corresponding to the phase difference 0 of the amplitude characteristic above. And G
_The phase difference between the numerically controlled oscillator 119 and the phase difference between _I and G _Q is measured. This phase difference is stored in advance as a unique value for each satellite.

In the following, the phase of a carrier is measured for a plurality of satellites, the measured phase of the carrier is compared between a plurality of receivers, and kinematic positioning for measuring the relative positions of the plurality of receivers is performed. It is an explanation of a method of measuring a carrier phase.

First, tracking is performed on the carrier of the satellite signal and the pseudo noise code. At the same time as measuring the relative position, the numerically controlled oscillator
Measure the phase of 119. At the same time, to measure G _I and G _Q at the timing corresponding to the phase difference 0 of the amplitude characteristic.
To match this timing, the pseudo noise code is tracked so that the average value EI of the amplitude becomes zero. And G _I
After correcting the measured phase of the numerically controlled oscillator 119 by an amount corresponding to the phase that can be obtained by G _{Q, the} previously stored phase difference corresponding to the satellite being tracked is corrected in reverse. The corrected phase is output as an observation value of the carrier phase.

As described above, according to the sixth embodiment of the present invention, the reception signal whose sign is inverted in the sign state is sampled at a timing having a fixed time difference from the timing of the pseudo noise code. A GPS receiver that measures the phase difference between the carrier of the received signal at the sampled timing and the local oscillation signal with the in-phase component and the quadrature component of the local oscillation signal that is the sampled reception signal, The phase difference of the carrier wave is measured in advance near the rising edge of the pseudo noise code, and when measuring the phase of the carrier wave, the phase measured by the means for measuring the phase difference with respect to the phase of the local oscillation signal is used. A correction is made with a phase difference, and further a reverse correction is made with the phase difference previously measured for each satellite to obtain the carrier phase of the observed satellite signal, so that the position of the carrier wave near the rising edge of the pseudo-noise code is obtained. However, even when there is a slight deviation from the average phase, the relative position can be measured accurately even when the relative position is measured with a receiver using another method. As in the case of the embodiment, an excellent effect is obtained in that a carrier phase of a satellite signal having little influence of multipath can be measured.

(Seventh Embodiment) The configuration of the seventh embodiment is the same as that of the fourth embodiment in FIG. 9, but the operation of the control unit 124 is different. The general operation is also the same as that of the sixth embodiment, and the difference will be described below.

First, when it is determined that there is no multipath,
Measuring the G _I and G _Q similarly to the sixth embodiment of the timing corresponding to the phase difference 0 of the amplitude characteristic above. And G
_The phase difference between the numerically controlled oscillator 119 and the phase difference between _I and G _Q is measured. This phase difference is stored in advance as a unique value for each satellite.

The following is a description of a method of measuring the phase of the pseudo noise code for a plurality of satellites and measuring the position using the phase of the pseudo noise code measured. First, similarly to the above-described sixth embodiment, tracking is performed on a carrier wave and a pseudo noise code of a satellite signal. And at the timing of measuring the position,
Measuring the G _I and G _Q at the timing corresponding to the phase difference 0 of the amplitude characteristic. And the phase difference between G _I and G _Q ,
The previously stored phase difference corresponding to the satellite being tracked is compared. When the difference between the two phase differences exceeds a predetermined value, it is determined that multipath has been affected, and a flag is set in the same manner as in FIG. 5 or FIG. 6 (see the flag-on process in step 212). This flag-on is maintained for a predetermined time after it is determined that the influence of the multipath has been exerted. When it is determined that the multipath is affected again while the flag is standing, the holding time is extended. Then, the position of the receiver is calculated with the phase of the pseudo-noise code excluding the observation result affected by the flag standing.

As described above, according to the seventh embodiment of the present invention, the multipath is determined based on the change of the carrier wave phase in the chip of the pseudo-noise code, so that the carrier wave phases of the reflected wave and the direct wave are different. The effect can be detected if
Unlike the second embodiment or the second embodiment, it is possible to detect the reflected wave and the direct wave even if the carrier wave phase difference does not change. Even if the signal is received, the observation result of this satellite is excluded, so that an excellent effect can be obtained in that high accuracy of the position can be obtained without being affected by multipath.

(Eighth Embodiment) The configuration of the eighth embodiment is the same as that of the fourth embodiment shown in FIG. 9, but the operation of the control unit 124 is different. In the present embodiment, in addition to the operation of the control unit 124 in any of the above-described first to third embodiments, pseudo noise is individually assigned to each satellite similarly to the above-described seventh embodiment. The carrier phase difference is measured in advance near the rising edge of the code, and when measuring the position, the phase difference of the carrier wave is measured again near the rising edge of the pseudo-noise code, and the phase difference stored in the corresponding satellite is By comparing, the influence of the multipath is determined, and the most severe condition among a plurality of evaluation results, such as multipath flag-on, multipath pseudo noise code phase accuracy evaluation, is selected. Based on the condition, the position is measured using the phase of the pseudo-noise code. In the first to third embodiments, the influence of the multipath can be detected with high sensitivity if there is a change in the state of the multipath. On the other hand, in the seventh embodiment, if the reflected wave and the direct wave have different carrier wave phases, the detection can be performed. Therefore, most of the multipath states can be detected by a combination of the two.

As described above, according to the eighth embodiment of the present invention, the above-described first to third embodiments and the seventh embodiment are combined to form a plurality of The strictest conditions are selected from the path evaluation results, and the observation results of the satellite signals affected by multipath can be more reliably eliminated or the weights can be changed, resulting in higher position accuracy. An excellent effect can be obtained in that

In the first embodiment, the operation of the second filter for time-integrating the correction amount of the phase is initialized to 0, and the integration is continuously performed. However, the present invention is not limited to this. Instead, the integral value of the arithmetic processing of the second filter can be attenuated with a long time constant.

In the second embodiment, step 21 for initializing the operation of the second filter is executed.
Although the period of the time determination process in 5 is set to 5 minutes, the present invention is not limited to this. Depending on the conditions for installing the receiver, the cycle of the change of the multipath changes, and this cycle is assumed to be long, and it is appropriate to make the cycle larger than half. Further, the period can be adjusted according to the magnitude of the maximum value M.

In the third embodiment described above, in the error evaluation process in step 217, 3/4 of the maximum value M is used as the error evaluation value, but the present invention is not limited to this. It is also possible to determine the characteristics of the receiver by an experiment, determine a table or an approximate expression from the obtained results, and relate the maximum value M to the evaluation value of the error by another method.

In the fourth embodiment, the timing at which the filter 136 samples the signal is the same as the timing at which the filter 136 samples the signal at the rising edge of the pseudo noise code. However, the present invention is not limited to this. . Any value can be set as long as it is near the rising portion of the pseudo noise code. But,
The earlier the timing, the less likely it is to be affected by multipath, but the signal strength decreases and the accuracy of the phase to be measured decreases.

Furthermore, in the above-described fourth embodiment, a mixer 135 and a filter 136 are newly added, and the received signal is sampled at the rising edge depending on whether the pseudo noise code is 1 or 0. Not done. Similar observations can be made near the timing corresponding to -1 chip of the characteristic of the average value EI of the amplitude in FIG. However, this method can be shared by the signal processing circuits, but the frequency of sampling is reduced to about half.

Further, the timing of the reference clock that precedes and follows the timing to be sampled is selected, and the amplitude of the received signal at the timing to be sampled is obtained by weighting. However, the present invention is not limited to this. The weighting can also be eliminated by increasing the frequency of the reference clock sufficiently.

Further, the accumulator, the correlator, the oscillator and the like are described as individual circuits, but the same function may be realized by numerical calculation by a microprocessor or the like.

Further, the NA operated by the United States
In the example described above, a GPS receiver that measures the amplitude of a signal in association with a pseudo-noise code that receives a signal of a VSTAR satellite is used.
It will be apparent that the present invention can be similarly applied to a receiver such as a LONASS satellite that measures the phase of a spread spectrum signal and measures the time indicated by the satellite signal to determine the position.

[0109]

As described above, according to the present invention, a first filter for obtaining a correction amount of a code phase for tracking a pseudo-noise code of a satellite signal, and a phase of the pseudo-noise code based on the correction amount of the phase. A pseudo-noise code tracking filter constituted by a correction means is provided with a second filter for time-integrating the amount of phase correction, and means for determining the effect of multipath based on the amplitude of the time-integrated result. It is determined by the means for determining the influence of the multipath that the phase of the noise code is changed due to the influence of the multipath, and the receiver is determined by the phase of the pseudo-noise code that excludes the affected observation result. By calculating the position, there is obtained an effect that high position accuracy not affected by multipath can be realized by a very simple process.

The present invention also provides a local oscillator for generating a local oscillation signal that tracks a carrier signal, means for converting the frequency of a received signal with the local oscillation signal, and converting the frequency-converted received signal to the timing of a pseudo-noise code. On the other hand, at a timing having a certain time difference, means for sampling the received signal whose sign is inverted in the sign state, and the in-phase component and the quadrature component of the local oscillation signal, which is the sampled received signal, A means for measuring the phase difference between the carrier of the received signal and the local oscillation signal at the sampled timing is provided.
By correcting the phase of the local oscillation signal with the phase difference measured by the means for measuring the phase difference to obtain the carrier wave phase of the observed satellite signal, the influence of the reflected signal delayed in the measurement of the carrier wave phase is reduced. It is possible to measure the phase difference of the carrier wave near the rising edge of the pseudo-noise code for each satellite in advance and measure the phase difference of the carrier wave again near the rising edge of the pseudo-noise code when measuring the position. By comparing with the stored phase difference, effects such as the effect of multipath can be determined.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a GPS receiver that measures a signal amplitude in association with a pseudo-noise code according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing a configuration of a correlator which is a component of a GPS receiver that measures a signal amplitude in association with a pseudo-noise code according to the first embodiment of the present invention;

FIG. 3A is a diagram illustrating a pseudo-noise code preceding by eight reference clocks according to the first embodiment of the present invention;
(B) A diagram for explaining a pseudo-noise generation code generated by the pseudo-noise generator according to the first embodiment of the present invention. (C) A signal output by the logic circuit 129 according to the first embodiment of the present invention. FIG. 4D is a diagram for explaining a period in which the filter 134 in the first embodiment of the present invention integrates the output of the mixer 133, and FIG. 4E is a diagram for explaining an integration period in the first embodiment of the present invention. A diagram for explaining a signal for identifying the first half and the second half,

FIG. 4 is an amplitude characteristic obtained by sampling a received signal at a timing at which a pseudo-noise code changes,

FIG. 5 is a flowchart illustrating a method of tracking a pseudo-noise code in the first embodiment of the present invention;

FIG. 6 is a flowchart illustrating a method of tracking a pseudo-noise code according to the second embodiment of the present invention;

FIG. 7A shows a second embodiment according to the first embodiment of the present invention.
(B) a diagram illustrating a signal of an operation output of a second filter according to the second embodiment of the present invention;

FIG. 8 is a flowchart illustrating a method of tracking a pseudo-noise code in the third embodiment of the present invention;

FIG. 9 is a block diagram showing a configuration of a correlator which is a component of a GPS receiver that measures a signal amplitude in association with a pseudo-noise code according to a fourth embodiment of the present invention;

10A is a diagram illustrating an amplitude characteristic obtained by sampling a received signal in accordance with a timing at which a pseudo noise code changes according to a fourth embodiment of the present invention, and FIG. 10B is a diagram illustrating a fourth embodiment of the present invention. Amplitude characteristics obtained by sampling the received signal in a multipath state according to the timing at which the pseudo-noise code changes,

FIG. 11 is a block diagram showing a configuration of a conventional GPS receiver.

[Explanation of symbols]

 101 GPS satellite 102 Antenna 103, 107, 113, 131, 134, 136 Filter 105, 111 Local oscillator 106, 112, 120, 130, 133, 135 Mixer 110, 127, 128 Latch 116 Pseudo noise generator 117 Correlator 118 , 121 Switch 119 Numerically Controlled Oscillator 122 Adder 123 RAM 124 Controller 125, 126 Counter 129 Logic Circuit 132 Weighter

Claims (8)

[Claims] 1. A local oscillator for tracking a carrier of a satellite signal, a pseudo-noise generator for generating a pseudo-noise code unique to a satellite, and controlling a phase of the pseudo-noise generator according to a phase change of the local oscillator. Means for controlling the phase difference between the pseudo-noise code included in the satellite signal and the pseudo-noise code generated by the pseudo-noise generator to be constant, and a correlator for measuring the phase difference of the pseudo-noise code, A first filter for inputting the measured phase difference to obtain a code phase correction amount for correcting the phase difference of the pseudo noise code, a unit for correcting the phase of the pseudo noise code by the correction amount, A second filter for time-integrating the quantity, and means for determining the effect of multipath on the basis of the amplitude of the time-integrated result. A GPS receiver, wherein the GPS receiver calculates the position of the receiver with the phase of the pseudo-noise code by excluding the received observation result. 2. A second filter for time-integrating the correction amount of the code phase, a means for judging the influence of multipath based on the amplitude of the time-integrated result, and a means for judging that a predetermined time has elapsed. 2. The GPS receiver according to claim 1, wherein the second filter is periodically initialized according to the determination. 3. A means for evaluating a phase measurement error of a pseudo-noise code due to the influence of multipath by using an amplitude output from a second filter for time-integrating the correction amount of the code phase. 3. The GPS receiver according to claim 1, wherein a position of the receiver is obtained by an observation value of a phase of the pseudo noise code by a least square method weighted using an evaluation value. 4. A local oscillator for tracking a carrier of a satellite signal, a pseudo-noise generator for generating a pseudo-noise code unique to a satellite, and controlling a phase of the pseudo-noise generator according to a phase change of the local oscillator. Means for controlling a phase difference between a pseudo-noise code included in a satellite signal and a pseudo-noise code generated by the pseudo-noise generator to be constant, and frequency conversion for orthogonally converting a received signal with the local oscillation signal. Means for generating a timing having a fixed time difference with respect to the timing of the pseudo-noise code generated by the pseudo-noise generator, and a reception signal output by the frequency converter having its sign inverted in the state of the code. Means for sampling a signal, and an in-phase component and a quadrature component with respect to the local oscillation signal, which are the sampled received signal, and a carrier wave of the received signal at the sampled timing and Means for measuring the phase difference of the local oscillation signal, and correcting the phase of the local oscillation signal by the phase difference measured by the means for measuring the phase difference to obtain an observation value of the carrier wave phase of the satellite signal. GP characterized by
S receiver. 5. A local oscillator for tracking a satellite signal carrier, a pseudo-noise generator for generating a pseudo-noise code unique to a satellite, and controlling the phase of the pseudo-noise generator according to a phase change of the local oscillator. Means for controlling a phase difference between a pseudo-noise code included in a satellite signal and a pseudo-noise code generated by the pseudo-noise generator to be constant, and frequency conversion for orthogonally converting a received signal with the local oscillation signal. Means for generating a timing having a fixed time difference with respect to the timing of the pseudo-noise code generated by the pseudo-noise generator, and a reception signal output by the frequency converter having its sign inverted in the state of the code. A means for sampling the signal; if the sampled received signal is of sufficient strength to track the carrier, the component of the sampled received signal corresponding to the quadrature component of the local oscillation signal; The local oscillation signal is controlled so as to be small, and if the sampled received signal is not sufficiently strong, the local oscillation signal is controlled by a signal obtained by multiplying the received signal by a pseudo noise code and then performing time integration. GPS receiver characterized by the above-mentioned. 6. A carrier phase difference is measured in advance near the rising edge of the pseudo noise code, and the measurement result is held for each satellite.
The phase difference measured by the in-phase component and the quadrature component with respect to the local oscillation signal, which is a sampled reception signal, is corrected in reverse by the stored phase difference of the corresponding satellite, and then the phase of the local oscillation signal is corrected. 5. The GPS receiver according to claim 4, wherein a carrier wave phase of the observed satellite signal is used as the carrier phase. 7. A local oscillator for tracking a satellite signal carrier, a pseudo-noise generator for generating a pseudo-noise code unique to a satellite, and controlling the phase of the pseudo-noise generator according to a phase change of the local oscillator. Means for controlling a phase difference between a pseudo-noise code included in a satellite signal and a pseudo-noise code generated by the pseudo-noise generator to be constant, and frequency conversion for orthogonally converting a received signal with the local oscillation signal. Means for generating a timing having a fixed time difference with respect to the timing of the pseudo-noise code generated by the pseudo-noise generator, and a reception signal output by the frequency converter having its sign inverted in the state of the code. Means for sampling a signal, and an in-phase component and a quadrature component with respect to the local oscillation signal, which are the sampled received signal, and a carrier wave of the received signal at the sampled timing and Means for measuring the phase difference of the local oscillation signal is provided, the phase difference of the carrier is measured in advance near the rising edge of the pseudo-noise code, and the measurement result is held for each satellite individually.
When measuring the position, the phase difference of the carrier is measured again near the rising edge of the pseudo-noise code, and the effect of multipath is determined by comparing with the stored phase difference of the corresponding satellite. A GPS receiver, wherein the position of the receiver is calculated based on the phase of the pseudo noise code by excluding an affected observation result. 8. In addition to the means for determining the influence of multipath or the means for evaluating the phase measurement error of a pseudo-noise code due to the influence of multipath, a local oscillation signal is used. A frequency converter for orthogonally transforming a received signal, a means for generating a timing having a fixed time difference with respect to the timing of a pseudo-noise code generated by a pseudo-noise generator, and the sign is inverted in the state of this code. Means for sampling the received signal output by the frequency converter, and in-phase and quadrature components with respect to the local oscillation signal, which is the sampled received signal, the carrier of the received signal at the sampled timing and the local oscillation Means for measuring the phase difference of the signal, the phase difference of the carrier wave is measured in advance near the rising edge of the pseudo noise code, the measurement result is held for each satellite individually, When measuring the phase difference of the carrier near the rising edge of the pseudo-noise code again and comparing it with the stored phase difference of the corresponding satellite to determine the effect of multipath, The GPS receiver according to any one of claims 1 to 3, wherein a strictest condition is selected from among the evaluation results.